Field of the Invention
Embodiments of the present invention generally relate to the field of safety detection technology, and in particular, to sample injection device and method for sample collection and sample thermal desorption, and a trace detection apparatus, which are capable of performing real-time collection and pre-concentration of volatile substance, semi-volatile substance, surface contaminant or the like, and which are suitable for fast sample collection and injection for Gas Chromatograph (GC), Ion Mobility Spectrometry (IMS), Gas Chromatography-Ion Mobility Spectrometry (GC-IMS) combination spectrometer or the like.
Description of the Related Art
Ion Mobility Spectrometry (IMS) technology has advantages of simple structure, high sensitivity, and fast analysis speed. It is able to achieve a fast trace (in ppb order of magnitude) detection on a substance under atmospheric pressure or near atmospheric pressure, and is very suitable for in-field use. Accordingly, IMS is widely applied for detection or inspection in various aspects including toxic chemical, narcotic drugs, explosives, environments, etc. However, during detection of mixtures, the IMS, as a detection instrument alone, encounters the following problems: (1) due to problems on the manufacturing process, currently commercial IMS only has a resolution ratio of about 30, which is difficult in differentiating chemical compounds having similar migration rates from one another; (2) ions from some chemical compounds undergo complicate reaction and annihilate each other in the ionization zone; (3) the IMS has a relatively lower dynamic range, so that, when there is/are one or several type(s) of chemical compounds with greatly large concentration(s), generations of ions of other types of chemical compounds will be adversely affected, which results in missed detection. Based on the above reasons, it is prone to trigger of false alarm or failing of alarm when a complex mixture having many types of chemical compounds is detected by the IMS.
Gas chromatography—ion mobility spectrometry (GC-IMS) combination technology has an excellently separation ability on complicated sample, and is capable of performing a pre-separation on the mixture, to separate the mixture into single components to be detected by the IMS. This combination technology will greatly enhance accuracy of the detection on the mixture. Conventional GC's analysis time is in order of magnitude of ten minutes or more, so it is difficult to meet demands on on-site fast detection. In recent years, fast GC technology has been developed rapidly, and its separation time (of tens of seconds—minutes) is greatly shortened compared to conventional GC. Fast GC-IMS, on one hand, inherits the separation ability of the GC, and on the other hand, succeeds to high sensitivity, fast response speed characteristics of the IMS, accordingly, it is capable of detecting complex components of the sample with a detection limit that is superior to the ppb order of magnitude and a detection time from a few minutes to tens of minutes. In addition, the fast GC-IMS reflects full advantages in the aspects of miniaturization and portable, is very suitable for on-site fast detection of a sample including complex components. This technology will play a powerful role in fields including anti-terrorism and riot control, drug smudging, environmental monitoring, food safety, and so on.
Sample injector is an integral part of a trace analytical instrument. Main sampling modes for a separate IMS comprise a wipe sampling thermal desorption mode and a direct sampling thermal desorption mode. The wipe sampling mode generally includes: wiping a substance to be detected by using a high temperature resistant wiping paper with a certain flexibility, and then, the sampling paper is put into a slot of the thermal desorption sample injector so that the substance adhered to the sampling paper is thermally desorbed by heating. This mode is only suitable for the sampling on surface contaminants, but is not suitable for the direct sampling on volatile or semi-volatile substances. In addition, the GC has sample injection requirements, which are different from those of the IMS, including rapid gasification of the sample's components, and rapid, accurate and quantitative application on the GC's column head after being mixed with the carrier gas. Accordingly, the existing IMS sample injection methods are not suitable for the GC-IMS in principle or in the sampling efficiency.
For a conventional GC sample injector, split/splitless sampling modes are used generally for solution samples; in these modes, however, not only interference of sample matrix on analysis needs to be considered, but also interference of sample solvents on analysis needs to be considered. Meanwhile, the sample further needs to be subject to a complicated pre-treatment, which is not suitable for on-site fast detection. Although a currently widely used head space sample injection does not require a complicated pre-treatment, it still “destructively” obtains a certain amount of sample, so it is not suitable for fast on-site detection for the trace gas without unpacking.
In a word, conventional IMS and GC technologies have low efficiency in sample collection and sample injection, low collection speed, and requires unpacking, which is not suitable for fast GC-IMS on-site detection.